Generally speaking, thermal printing industry is lacking a reliable way of media or ribbon width detection, which would be automatic and accurate at the same time.
Standard means of width detection often offer only a part of a solution, by focusing either on automation, or on accuracy. For example, in U.S. Pat. No. 6,352,332 by Walker, a media edge detection method and apparatus uses a single scanning-carriage-based optical sensor to determine a reflectance profile of the paper and pivot the carriage while scanning across the paper. The invention suggests recursively converging the data to get a cumulative error. Japanese Pat. No. 6,354,267 by Takeo discloses a method for detecting the presence of paper using linear pattern of reflective optical sensor disposed over entire width of printing paper or inlet or guide member. Japanese Pat. No. 60,233,504 by Akira et al. discloses a method of paper width detection using LED elements placed at particular intervals. Similarly to the U.S. Pat. No. 6,354,267 patent, this invention does not offer means for correcting the errors encountered in calculating the width. U.S. Pat. No. 8,646,869 by Yamazaki discloses a recording position error measurement apparatus, and an algorithm for calculating the position error measurements in image-based analysis for calculating the width, but it does not mention applying optical sensors for detecting paper width. Moreover, width detection solutions, such as described above, tend to suffer from a high cost of implementation, poor width resolution, or even incomplete automation, requiring some level of user intervention or parts adjustment.
Some inventions are rather automatic, some are rather accurate, but neither of them offers automation and accuracy at the same time. Therefore, a need exists for an automatic and accurate media and ribbon width detection method and apparatus.